Retaining walls are structures that typically hold back earth material. They typically resist the lateral forces exerted by earth material, such as soil. In some cases, retaining walls are used to stabilize earth material that has a sloping surface. Retaining walls are also used to retain earth material at a different elevation than an adjacent ground surface, for aesthetic or structural purposes.
Many retaining walls are constructed by vertically stacking a plurality of retaining wall blocks. U.S. Pat. No. 5,816,749 to Bailey, II discloses a modular wall block. The modular wall block has a pair transverse projections extending upwardly from its top surface, spaced from each other by an upwardly opening groove. The modular wall block also has a pair of downwardly opening, transverse grooves spaced from each other by a downwardly extending projection. When one modular wall block is stacked onto another, the downwardly extending projection of the higher block may be received in the upwardly opening groove of the lower block to offset the front faces of the two blocks. In another stacked configuration, the pair of upwardly extending projections of the lower block are received within one of the pair of downwardly opening, transverse grooves of the higher block, to align the front faces of the two blocks.